Theoretical Studies of Electronic Structure and Dynamical Aspects of Electronically Nonadiabatic Processes

本项目由美国国家科学基金会理论与计算化学计划资助，主要研究激发态下玻恩·奥本海默击穿的计算方法及其在光化学途径研究中的应用。利用多构型自洽场（MCSCF）波函数的解析能量导数方法定位低能表面交叉和避交。该理论应用于研究与气体激光和大气化学有关的自旋禁止，非绝热过程，如臭氧的光解，波长低于310 nm，以产生单线态和三重态产物。本研究的中心目标是发展电子激发态分子的基本化学反应的量子力学理论，通常是由吸收适当频率的光引起的。这些光化学反应的一个重要特征是，这些受激分子可以从一个电子态跳到另一个电子态，并伴随着电子、振动和平移自由度之间的能量转移。这个理论研究项目为光谱和动力学实验揭示的分子过程提供了更深入的了解。本项目发展广泛适用于光化学过程的基本理论工具，特别是适用于大气中臭氧消耗的计算机模型。

This project, supported by the NSF Theoretical and Computational Chemistry Program, develops computational methods for the study of Born Oppenheimer breakdown in excited electronic states, and their application to the study of photochemical pathways. Methods using analytic energy derivatives for multiconfiguration self-consistent field (MCSCF) wavefunctions are employed to locate low energy surface crossings and avoided crossings. The theory is applied to the study of spin-forbidden, non-adiabatic processes relevant to gas lasers and atmospheric chemistry such as photodissociation of ozone, at wavelengths below 310 nm, to produce both singlet and triplet products. The central goal of this research is the development of the quantum mechanical theory of elementary chemical reactions of molecules in electronically excited states, usually resulting from the absorption of light of an appropriate frequency. An important feature of these photochemical reactions is the fact that these excited molecules can jump from one electronic state to another with a concomitant transfer of energy between electronic, vibrational, and translational degrees of freedom. This theoretical research project provides deeper insight into such molecular processes revealed by spectroscopic and kinetic experiments. This project develops basic theoretical tools widely applicable to photochemical processes, in particular, to computer models of ozone depletion in the atmosphere.